理解CountDownLatch

字面意思是倒计时类
类名其实说的很形象，倒数到0时线程解除阻塞，继续往下执行

测试类
public class TestCDL {
private static CountDownLatch countDownLatch = new CountDownLatch(3);

public static void test(){

Thread thread = new Thread(){
@Override
public void run() {
try {
//阻塞在这儿了
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
System.out.println("after await" + this.getId());
}
}
};

thread.start();

//count = 3
System.out.println("Count:" + countDownLatch.getCount());
countDownLatch.countDown();

//count = 2
System.out.println("Count:" + countDownLatch.getCount());

countDownLatch.countDown();
countDownLatch.countDown();

//count = 0 ；线程解除了阻塞
System.out.println("Count:" + countDownLatch.getCount());
}

public static void main(String[] args) {
test();
}
}

评论

1 楼 mercyblitz 2010-07-10  

CountDownLatch实现很简单，我很佩服Doug Lea设自己的AbstractQueuedSynchronizer。其利用状态信息控制pack和uppack.